To support packet data communication in communication networks between wireless mobile stations, even called mobile stations, in a radio network, and packet data networks, different packet-based communication technologies have been developed, such as GPRS (General Packet Radio Service), WCDMA (Wideband Code Division Multiple Access), HSPA (High Speed Packet Access) and LTE (Long Term Evolution).
For setting up a data connection between a wireless mobile station (MS) and a packet data network in a GPRS network, a GPRS attach followed by a Packet Data Protocol (PDP) context activation is performed. In the GPRS attach, the MS connects to the core network. This means that the MS is authenticated and can access GPRS services. Thereafter, when the user wants to start communicating with a packet data network, such as the Internet or an Intranet, a PDP context is activated. A PDP context defines a tunnel that is set up between the core network and the MS.
FIG. 1 shows the procedure of activating a PDP context between a mobile station 102 and the core network nodes Serving GPRS support node (SGSN) 106 and Gateway GPRS support node (GGSN) 108. The mobile station 102 is connected to the core network via a radio access network (RAN) 104. The RAN comprises a plurality of NodeBs, and Radio Networks controllers (RNC), each controlling a subgroup of the plurality of NodeBs.
An activated PDP context contains the information required to map the core network service to the radio access service, i.e. a radio access bearer (RAB) fulfilling the quality requested, and the IP address of the MS.
The PDP context activation procedure according to the 3GPP standard TS 23.060 version 10.5.0 starts by the MS 102 sending an Activate PDP context request message 1.1 to the SGSN 106. The Activate PDP context request message comprises the following parameters: Network Layer Service Access Point Identifier (NSAPI), Transaction Identity (TI), PDP Type, PDP Address, Access Point name, Quality of Service (QoS) requested, PDP configuration options, and request type. The parameter Access Point Name is used to select a reference point to a certain external packet data network and/or a service that the subscriber wishes to connect to. Access Point Name may be a logical name referring to the external packet data network that the subscriber wishes to connect to. The parameter QoS Requested indicates a desired QoS profile. The parameter PDP Configuration Options may be used to request optional PDP parameters from the GGSN.
When the SGSN 106 has received the Activate PDP context request message, it validates the Activate PDP context request using PDP Type, PDP Address, and Access Point Name provided by the MS and PDP context subscription records. Further, the SGSN selects reference point to the external network based on the Access Point Name. The SGSN also derives a GGSN address and maps the Access Point Name to the GGSN address. The SGSN creates a Tunnel Endpoint Identifier (TEID) for the requested PDP context.
Thereafter, the SGSN 106 sends a Create PDP context request message 1.2 to the GGSN 108, the request message comprising PDP Type, Access Point Name, TEID etc. The GGSN 108 then creates a new entry in its PDP context table and generates a charging ID to allow the GGSN to route PDP packet data units between the SGSN and the packet data network, and to start charging.
The GGSN then responds by sending a Create PDP context response message 1.3 back to the SGSN 106, the response message comprising TEID, PDP Type, a negotiated QoS etc. The SGSN 106 then uses the information received to set up 1.4 a Radio access bearer (RAB) from the SGSN to the MS 102.
Eventually, the SGSN 106 inserts the NSAPI, a GGSN address and the PDP address received from the GGSN in its PDP context. It also selects radio priority and packet flow ID based on QoS Negotiated, and returns an Activate PDP Context Accept message 1.5 to the MS 102, the accept message comprising PDP Type, PDP Address, TI, QoS Negotiated, radio priority, packet flow ID and protocol configuration options. The SGSN is now able to route PDP packet units between the GGSN and the MS.
In other words, when the PDP context has been set up, there is a connection between the core network and the MS over which data traffic can be sent. All data sent over this connection will have the same priority. For example, the scheduling queue in the nodeB will not make any difference between packets for prioritizing packets differently.
Although, there is an interest to prioritize data differently. For example, real-time communication, such as voice communication, needs higher priority than data communication, such as web surfing.
If, for example, a user that has an ongoing web surfing session decides to set up a voice connection, there will be two simultaneous data flows. In this case, the voice connection should have higher priority, or in other words higher Quality of Service, than the web surfing session because voice is more delay sensitive than the web surfing session. If only one PDP context is activated, all data has the same priority. It is possible to change the QoS for a PDP context, but if different data flows needing different QoS are to be transmitted more or less simultaneously it does not help changing QoS to prioritize between the two flows.
To solve this, a second PDP context can be set up having a different QoS than the first PDP context. This means that the mobile station now have two PDP contexts to the core network set up simultaneously, including having two separate radio access bearers set up between the RAN and the MS. The second PDP context can e.g. be used for voice communication and the first PDP context can e.g. be used for the web surfing session. The first and the second PDP context can be given different scheduling priorities, based on the QoS values, wherein the voice communication normally would have higher priority than the web surfing session. Such a second PDP context is set up in the same way as described above in relation to FIG. 1. Although, the activation of the second PDP context can be initiated by the network by telling the MS to start the activation PDP context activation procedure, by sending an Activate Second PDP context request message.
As shown, at least two different PDP contexts have to be set up between the core network and the mobile station for ensuring the possibility to give different priorities to different data flows to and from the mobile station.
Although, there may be reasons when the radio access network would like to be able to support different priorities to different data flows without having to involve the core network. One scenario where this could be beneficial is if the core network and the radio access network are owned by different operators. Another reason is if there is a data flow coming from a cache memory in the RAN. In the latter case, the cached data flow could be more quickly distributed if the core network is not involved.